共查询到20条相似文献,搜索用时 484 毫秒
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CuO作为催化剂的主要活性组分已应用于氧化、加氢、CO和碳氢化合物的燃烧,N0x还原等多种催化反应中,有关N0、CO在CuO上吸附的红外光谱研究已有一些报导.London和Bell曾研究CO和NO在CuO/SiO_2上的反应,他们根据红外光谱和动力学测量结果推测NO主要离解吸附于Cu~0上,而CO则吸附在Cu~+或Cu~(2+)上.Busca在未还原的CuO样品上,观测到CO在Cu~+上的红外吸收峰最强,从而认为体相为CuO的样品,铜在其表面主要由Cu~+并伴以Cu~(2+)构成.本文研究了CuO/γ-Al_2O_3上NO、CO单独、交替和共吸附时的低温红外光谱,证明当NO和CO共存时,NO选择吸附于Cu~(2+)上,而CO选择吸附于Cu~+上。 相似文献
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介孔Ce1-xZrxO2负载的Cu基催化剂在富氢条件下催化CO选择性氧化 总被引:1,自引:0,他引:1
采用多元醇为模板剂合成了介孔Ce1-xZrxO2(x=0.2,0.35,0.5)固溶体材料,并以其为载体负载CuO制备了Cu基催化剂.应用透射电子显微镜、X射线衍射、程序升温还原、程序升温脱附和N2吸附-脱附等技术对载体及催化剂进行了表征,并研究了Zr的取代比例x值对载体和Cu基催化剂性能的影响.结果表明,所有Ce1-xZrxO2样品均为介孔材料,其中Ce0.5-Zr0.5O2载体样品有较大的比表面积(181m2/g),CuO/Ce0.5Zr0.5O2催化剂样品在富氢条件下有较高的催化CO选择性氧化反应的活性和选择性.与其他催化剂样品相比,CuO/Ce0.5Zr0.5O2催化剂样品中形成的活性中心更多,分散性更好,对CO的吸附量更大,CO脱附温度更低,活性组分与载体的相互作用更强。 相似文献
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纳米SnO2微粉的制备与性能 总被引:25,自引:1,他引:25
纳米SnO_2微粉的制备与性能刘杏芹,陶善文,沈瑜生(中国科学技术大学材料科学与工程系合肥230026)关键词纳米微粉,二氧化锡,溶胶-凝胶法,气敏性能SnO2作为一种功能基体材料,在气敏、湿敏、光学技术等方面已有广泛的应用,而SnO2微粉或超微粉的?.. 相似文献
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采用离散变分Xα方法分别计算了CO和NO以C(或N)端顶位吸附在CuO(110)及Cu2O(110)表面上的基态势能曲线,结果表明:CO在Cu2O表面上的吸附强,而在CuO表面上的吸附弱;NO则在CuO表面上吸附强,在Cu2O表面上吸附弱.它们的吸附能的大小顺序为:CuO-NO>Cu2O-CO>Cu2O-NO>CuO-CO.对于CuO-NO(或CO)吸附体系,主要是Cu的3d轨道与吸附分子的2π轨道间的相互作用;对于Cu2O-CO(或NO)吸附体系,则主要是吸附质分子的5σ及2π分子轨道与其顶位Cu1的4s及4p轨道和侧位Cu2的3d轨道相互作用.本文通过吸附势能曲线、态密度分析、成键分析及电荷转移量和方向等方面对实验现象做了合理的解释. 相似文献
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CuO/Ce-Zr-La-O催化剂的表征及CO氧化活性 总被引:5,自引:3,他引:5
采用柠檬酸溶胶-凝胶法制备的Ce-Zr-La-O固溶体为载体,制备CuO/Ce-Zr-La-O催化剂,用XRD,Raman,TPR等实验技术对Ce-Zr-La-O固溶体及CuO/Ce-Zr-La-O的物相、Redox性能进行了表征。实验结果表明,Ce0.7Cr0.3-yLayO固溶体的还原性能与La含量有关,适量的La能促进固溶体的氧化还原。CuO的负载量为6%时,CuO/Ce0.7Zr0.15La0.15O的活性最高,高分散且与载体相互作用的CuO是CO氧化活性相。 相似文献
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聚酯酸酐的合成与表征 总被引:3,自引:0,他引:3
聚酸酐具有优良的表面溶蚀性能,作为药物控释体系材料得到广泛的应用.以对(2 羟基 乙氧基)苯甲酸和对(2 甲基 2羟基 乙氧基)苯甲酸分别与丁二酸酐,顺丁烯二酸酐和丁二酰氯反应得到六个含有酯基的新型二元酸单体,经熔融聚合得到聚酯酸酐.单体和聚合物经IR,1H NMR和元素分析等表征.研究了催化剂对聚合物结构的影响. 相似文献
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Y. K. Kim E. Y. Kim C. M. Whang Y. H. Kim W. I. Lee 《Journal of Sol-Gel Science and Technology》2005,33(1):87-91
Nanophase silica-titania particles were prepared by two different synthetic routes, namely, sol–gel and hydrothermal processing. The crystallinity and crystallographic phases, particle size and surface area of the materials were controlled by varying the calcination temperature, and/or the ratio of Si to Ti. It was determined by XRD that the crystallite sizes of SiO2-TiO2 prepared by sol–gel and hydrothermal processing decreased from 11 to 6 nm and 12 to 9 nm, respectively, as the mole fraction of silica was increased from 0.1 to 0.4. It is proposed that the presence of the amorphous silica suppresses the growth of anatase TiO2 grains and their phase transformation to rutile. The photocatalytic decomposition rate of 1,4-dichlorobenzene (DCB) in aqueous solution with the sol–gel derived SiO2-TiO2 powder prepared at 750 °C was about 10 ± 5% higher than that observed with Degussa P25, whereas the SiO2-TiO2 samples prepared by hydrothermal processing at 250 °C showed a slightly lower decomposition rate than P25. 相似文献
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G. A. El-Shobaky S. A. El-Molla S. A. Ismail 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(3):627-636
Copper and nickel oxide samples supported on MgO were prepared by wet impregnation method. The obtained solids were heated
at 350 °C and 450 °C. The extent of copper and nickel oxides was fixed at 16.7 mol%. The effect of g-irradiation (0.2-1.6
MGy) on the surface and catalytic properties of the solids were investigated. The techniques employed were XRD, nitrogen adsorption
at -196 °C and H2O2 decomposition. The results revealed that the g-irradiation up to 0.8 MGy of CuO/MgO-450 °C effected a measurable decrease
in the crystallite size of CuO phase with subsequent increase in its degree of ordering. Irradiation at a dose of 1.6 MGy
brought about a complete conversion of MgO into Mg(OH)2 during its cooling from 450 °C to room temperature via interacting with atmospheric water vapor. The S
BET and total pore volume of CuO/MgO precalcined at 350 °C and 450 °C increased progressively as a function of g-ray dose reached
a maximum limit at 0.8 MGy. Gamma-irradiation of NiO/MgO-450 °C solids up to 0.8 MGy increased the degree of ordering of MgO
and NiO phases without changing their crystallite size. The exposure of these solids to 1.6 MGy led to an effective transformation
of some of NiO (not dissolved in MgO lattice) into Ni(OH)2 via interacting with atmospheric water vapor during cooling from 450 °C to room temperature. Gamma-irradiation led to a measurable
increase in the S
BET and V
p of NiO/MgO system. Gamma-irradiation of the two investigated systems resulted in both increase and decrease in their catalytic
activities in H2O2 decomposition depending mainly on the irradiation dose and calcination temperature. This treatment, however, did not modify
the mechanism of the catalytic reaction, but changed the catalytic active sites without changing their energetic nature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Chira R. Bhattacharjee Debraj Dhar Purkayastha Nirmalendu Das 《Journal of Sol-Gel Science and Technology》2013,65(3):296-300
Tricobalt tetraoxide nanoparticles have been successfully synthesized following a ‘bottom-up’ approach by surfactant-free thermal decomposition of cobalt(II)-tartrate complex obtained by a modified sol–gel route. The synthesized complex was characterized by Fourier transform infrared (FT-IR) spectroscopy, elemental and thermogravimetric-differential thermal analysis (TG–DTA). The nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman studies. The powder XRD pattern furnished evidence for a face-centered cubic structure of Co3O4. With the rise in calcination temperature from 400 through 500 to 600 °C, the average crystallite sizes of Co3O4 were found to increase from 28 through 36 to 46 nm. The TEM image revealed a faceted morphology of the as-synthesized Co3O4 nanoparticles. The high-resolution TEM image indicated the interplanar separation to be 0.28 nm which corresponds to the (220) plane in face-centered cubic Co3O4. The electron diffraction (ED) pattern showed single-crystalline nature of the synthesized nanoparticles. Raman spectrum showed four characteristic peaks of Co3O4 which further confirmed the phasic purity of the material. 相似文献
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Won Young Jung Seung Hee Baek Seong Soo Park Gun-Dae Lee Euh Duck Jeong Hyun Gyu Kim Seong-Soo Hong 《Reaction Kinetics and Catalysis Letters》2007,91(2):233-240
The nanosized titania and TiO2/SiO2 particles were prepared by the microwave-hydrothermal method. The effect of physical properties TTIP/TEOS ratio and calcination
temperature has been investigated. The major phase of the pure TiO2 particle is of the anatase structure, and a rutile peak was observed above 800°C. In TiO2/SiO2 particles, however, no significant rutile phase was observed, although the calcination temperature was 900°C. No peaks for
the silica crystal phase were observed at either silica/titania ratio. The crystallite size of TiO2/SiO2 particles decreases as compared to pure TiO2 at high calcination temperatures. The TiO2/SiO2 particles show higher activity on the photocatalytic decomposition of orange II as compared to pure TiO2 particles. 相似文献
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A complete characterization of the calcination of precipitates obtained from a continuous operation was carried out in this study. The precipitate was obtained by reacting yttrium nitrate and ammonia solutions in a MSMPR reactor. It precipitated out as yttrium hydroxide nitrate hydrate, which has the general form Y2(OH)6-x(NO3)x·y H2O. This compound decomposed in consecutive steps with the last reaction occurring at 525°C.The calcination process was characterized by chemical analysis, X-ray diffraction analysis, DTA and TG. In addition, the physical characteristics of calcined powders, such as specific surface area, particle size distribution, pore volume distribution, X-ray crystallite size and conversion were measured as a function of calcination temperature and time. Finally, the kinetics of the reduction of surface area, the growth of crystallite size and conversion were also examined. 相似文献
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Three-dimensional (3D) hierarchical architectures are currently attracting worldwide interest owing to their fascinating morphology-dependent properties and potential applications. Herein we constructed SnO2 microspheres with 3D hierarchical flower-like architectures self-assembled with porous SnS2 nanosheets by a facile hydrothermal method with subsequent calcination. The chemical and physical properties as well as photocatalytic application of SnO2 microspheres were investigated. The size and morphology were examined with scanning electron microscopy and transmission electron microscopy. The phase and crystalline structure were determined with powder X-ray diffraction. The UV–Vis absorption property was determined with UV–Vis diffuse reflectance. The photocatalytic activities were evaluated with nitrogen monoxide (NO) decomposition under UV–Vis light irradiation. The effects of calcination temperature on morphology and NO decomposition were also studied. 相似文献
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A series of NixCo1-xCo2O4(0 ≤ x ≤ 1) spinel catalysts were prepared by the co-precipitation method and used for direct N2O decomposition. The decomposition pathway of the parent precipitates was characterized by thermal analysis. The catalysts were calcined at 500 °C for 3 h and characterized by powder X-ray diffraction, Fourier transform infrared, and N2 adsorption-desorption. Nickel cobaltite spinel was formed in the solid state reaction between NiO and Co3O4. The N2O decomposition measurement revealed significant increase in the activity of Co3O4 spinel oxide catalyst with the partial replacement of Co2+ by Ni2+. The activity of this series of catalysts was controlled by the degree of Co2+ substitution by Ni2+, spinel crystallite size, catalyst surface area, presence of residual K+, and calcination temperature. 相似文献
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Shu-Ping Wang Xiao-Ying Wang Xiu-Cheng Zheng Shu-Rong Wang Shou-Min Zhang Wei-Ping Huang Shi-Hua Wu 《Reaction Kinetics and Catalysis Letters》2006,89(1):37-44
Summary Copper oxide catalysts supported on Ce0.8Zr0.2O2 were prepared via an impregnation method and characterized by XRD and H2-TPR techniques. The catalytic activity of the samples for low-temperature CO oxidation was investigated by means of a microreactor-GC
system. The influence of calcination temperature, calcination time and different CuO content on the catalytic activity was
studied. TPR analysis indicated that well-dispersed CuO was responsible for the low-temperature CO oxidation. The results
of the investigation showed that the calcination temperature and CuO loadings had larger influence than the calcination time. 相似文献
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Ruby Chauhan Ashavani Kumar Ram Pal Chaudhary 《Research on Chemical Intermediates》2012,38(7):1443-1453
Undoped and silver-doped TiO2 nanoparticles (Ti1?x Ag x O2, where x?=?0.00?C0.10) were synthesized by a sol?Cgel method. The synthesized products were characterized by X-ray diffraction (XRD), particle size analyzer (PSA), scanning electron microscope (SEM), and UV?CVisible spectrophotometer. XRD pattern confirmed the tetragonal structure of synthesized samples. Average crystallite size of synthesized nanoparticles was determined from X-ray line broadening using the Debye?CScherrer formula. The crystallite size was varied from 8 to 33?nm as the calcination temperature was increased from 300 to 800?°C. The incorporation of 3 to 5% Ag+ in place of Ti4+ provoked a decrease in the size of nanocrystals as compared to undoped TiO2. The SEM micrographs revealed the agglomerated spherical-like morphology of particles. SEM, PSA, and XRD measurements show that the particles size of the powder is in nanoscale. Optical absorption measurements indicated a red shift in the absorption band edge upon silver doping. Direct allowed band gap of undoped and Ag-doped TiO2 nanoparticles measured by UV?CVis spectrometer were 3.00 and 2.80?eV, respectively, at 500?°C. 相似文献
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Studies of the surface wettability and hydrothermal stability of methyl-modified silica films by FT-IR and Raman spectra 总被引:1,自引:0,他引:1
Fourier transform infrared (FT-IR) and Raman spectroscopy were employed to study the hydrothermal stability and the influence of surface functional groups on the surface wettability of methyl-modified silica films. The surface free energy parameters of the silica films were determined using the Lifshitz-van der Waals/acid–base approach. The thermal decomposition mechanisms of the CH3 groups in the methyl-modified silica material are proposed. The results show that with the increase of methyltriethoxysilane (MTES)/tetraethylorthosilicate (TEOS) ratio, the surface free energy and surface wettability of the silica films decrease greatly. This is mainly because of the contribution of the acid–base term; the intensity of Si–CH3 groups increases at the expense of the intensity of O–H groups in the samples. The surfaces of the methyl-modified silica films exhibited predominantly monopolar electron-donicity. The contact angle on the silica film surface reaches its maximum value when calcination is performed at 350 °C. Thermogravimetric analysis implies that some low molecular weight species, such as H2, CH4, and C, are eliminated upon thermal decomposition of the –CH3 groups. The Si–CH3 and –CH3 vibrational bands diminish in intensity as the calcination temperature is increased, disappearing completely when the calcination temperature is increased to 600 °C. When the calcination temperature is increased to 750 °C, the free carbon and CSi4 species will be formed. 相似文献